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<table width="100%" summary="page for acidiq"><tr><td>acidiq</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Acifluorfen and diquat tested on Lemna minor.</h2>

<h3>Description</h3>

<p>Data from an experiment where the chemicals acifluorfen and diquat tested on Lemna minor. The dataset has 7 mixtures used in
8 dilutions with three replicates and 12 common controls, in total 180 observations.
</p>


<h3>Usage</h3>

<pre>data(acidiq)</pre>


<h3>Format</h3>

<p>A data frame with 180 observations on the following 3 variables.
</p>

<dl>
<dt><code>dose</code></dt><dd><p>a numeric vector of dose values</p>
</dd>
<dt><code>pct</code></dt><dd><p>a numeric vector denoting the grouping according to the mixtures percentages</p>
</dd>
<dt><code>rgr</code></dt><dd><p>a numeric vector of response values (relative growth rates)</p>
</dd>
</dl>



<h3>Details</h3>

<p>The dataset is analysed in Soerensen et al (2007). 
Hewlett's symmetric model seems appropriate for this dataset. 
</p>


<h3>Source</h3>

<p>The dataset is kindly provided by Nina Cedergreen, Department of Agricultural Sciences, 
Royal Veterinary and Agricultural University, Denmark.
</p>


<h3>References</h3>

<p>Soerensen, H. and Cedergreen, N. and Skovgaard, I. M. and Streibig, J. C. (2007) 
An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments, 
<em>Environmental and Ecological Statistics</em>, <b>14</b>, 383&ndash;397.
</p>


<h3>Examples</h3>

<pre>

## Fitting the model with freely varying ED50 values
## Ooops: Box-Cox transformation is needed
acidiq.free &lt;- drm(rgr ~ dose, pct, data = acidiq, fct = LL.4(),
pmodels = list(~factor(pct), ~1, ~1, ~factor(pct) - 1))

## Lack-of-fit test
modelFit(acidiq.free)
summary(acidiq.free)

## Plotting isobole structure
isobole(acidiq.free, xlim = c(0, 400), ylim = c(0, 450))

## Fitting the concentration addition model
acidiq.ca &lt;- mixture(acidiq.free, model = "CA")

## Comparing to model with freely varying e parameter
anova(acidiq.ca, acidiq.free)  # rejected

## Plotting isobole based on concentration addition -- poor fit
isobole(acidiq.free, acidiq.ca, xlim = c(0, 420), ylim = c(0, 450))  # poor fit

## Fitting the Hewlett model
acidiq.hew &lt;- mixture(acidiq.free, model = "Hewlett")

## Comparing to model with freely varying e parameter
anova(acidiq.free, acidiq.hew)  # accepted
summary(acidiq.hew)

## Plotting isobole based on the Hewlett model
isobole(acidiq.free, acidiq.hew, xlim = c(0, 400), ylim = c(0, 450))  # good fit

</pre>


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